Leakproof and siftproof package



Oct. 2, 1951 R A, FARRELL 2,569,851

LEAKPROOF AND SIFTPROOF PACKAGE Filed June 2l, 1949 Patented Oct. 2, 1951 UNITED STATES PATENT OFFICE LEAKPROOF AND SIFTPROOF PACKAGE Robert A. Farrell, Menasha, Wis., assignor to Marathon Corporation, Rothschild, Wis., a corporation of Wisconsin Application June 21, 1949, Serial No. 100,475

2 Claims. (Cl. 229-55) This invention relates to leakproof and siftproof packages and the method of making same. More specifically this invention relates to packages made from rectangular or tubular cartons having the open ends thereof sealed with a flexible closure membrane.

The present invention relates to an improvement of the package construction disclosed in copendingapplication Serial 686,537 filed July 26, 1946, now Patent 2,496,043, January 31, 1950, and provides very satisfactory leakproof and siftproof packages which can be produced eiliciently by mechanical equipment.

Further objects and advantages of the invention will be apparent from the following specification and drawings wherein:

Figure 1 is a perspective view of the package showing the ends sealed with a membrane,

Figure 2 is a sectional view taken on lines 2 2 of Figure 1,

Figure 3 is an enlarged perspective view of the package, partially broken away,

Figure 4 is a sectional view taken on lines I-I of Figure 2,

Figure 5 is a sectional view taken on lines 5-5 of Figure 2, and

Figure 6 is a fragmental vertical section of the completed filled package.

Referring to the drawings, the present invention is applicable to any conventional type of carton such as a folding rectangular or tubular type of carton having open ends and closure flaps Il as shown in Figure 1, which is preferably formed from a single blank. The blank is formed from any suitable carton stock having a caliper say of 0.018 in. suitably cut and scored along score lines 5 to provide side walls I0, each of which is provided with closure flaps Il at each end of the carton.

The tubular container is set up in any suitable manner manually or by equipment, and one end thereof is then completely sealed by a flexible membrane 20 as illustrated in Figure l. The membrane 20 is substantially rectangular in shape and of suitable dimensions so as to fully close the open end of the container, as well as to partially overlap over the closure flaps il as shown in Figure l. The membrane lis preferably cut out at the corners so that no free portions of the membrane extend between the flaps, and this also facilitates mechanical feeding when the membranes are used in roll form. The membrane may be formed of any suitable flexible sheet material such as paper, say 25-lb. basis wet-strength bleached 2 kraft having applied to one face thereof which is presented in contact with the carton a coating 25, say of a 20-lb. base weight of a co'mposition consisting of by weight of microcrystalline wax and 15% by weight of isobutylene polymer and having a viscosity when applied of not less than about 10,000 centipoises at C. The. membrane mayalso be formed of any other suitable self-sustaining sheet material suitably coated such as cellophane (regenerated cellulose). ethyl cellulose, cellulose acetate and the like. 'Ihe membrane may also be formed of self-sustaining thermoplastic films such as rubber hydrochloride (Plioiilm), wax-rubber films as disclosed in Patent No. 2,054,115, vinylidene chloride lms. films of copolymers of vinyl acetate and vinyl chloride, films of vinyl chloride and the like. The coating 30 on the membrane may also be formed of any suitable substance or composition depending upon the specific materials to be packaged, and requirements of waterproofness, moistureproofness, greaseproofness and the like. The coating, for example, may be made of a rubber and wax composition as disclosed in Patent No.

2,054,115; microcrystalline wax, and aluminum stearate compositions of the type disclosed in Patent No. 2,348,687; polyamid resins; ethyl cellulose; rubber hydrochloride, etc. The flexible membrane 20 is positioned in flat condition over the open end of the carton and then shaped in situ by any suitable means such as an expansible head as disclosed in copending application Serial No. 92,344 filed May 10, 1949, which will shape or form the membrane without rupturing same and depress the marginal portions 2| thereof and bring them into contact with the inner perimeter of the open end of the carton below the upper edge thereof and below the score lines upon which the respective closure flaps Il are hinged to the side walls I0. The exiblemembrane 20 is applied so as to present the coating thereon to the inner face of the carton and the closure flaps. The walls and flaps of the carton are rigidly supported by any suitable means and heat and pressure are applied to the membrane so as to seal or adhere the marginal portions 23 thereof tothe closure flaps in contact therewith, as well as the depressed portions 2l to the inner faces of the side walls of the carton. A suitable applying means may be used, such as an expanding head, so as to apply sufficient pressure not only at the depressed portions 2| of the membrane, but also at e'ach or the corners .of the carton lwhere leakage is more likely to occur when liquid contents are placed in the carton. The flexible memb-rane 20 is preferably heat-sealed by application of suitable heat and pressure to the flaps and corners of the carton while the flaps and corners are rigidly supported. The flexible membrane 20 of suitable contour and dimensions is thus depressed around the entire end opening of the carton by uniform manipulation of the membrane so as to eliminate any wrinkling or buckling. In order to insure that no leakage occurs at .the corners 6 the score lines 5 do not extend to the ends of the carton but stop short therefrom for a length B, as indicated in Figure 3, so that the inner periphery of the carton adjacent each open end is substantially smooth and continuous about its entire periphery. Thus as shown in Figures 3 and 5, the inner periphery of the carton about the body region is interrupted by the inwardly protrudlng score line 5 which forms a small ridge at the corners of the carton as shown in Figure 5. However, by having the score lines 5 terminate a short distance from each of the ends of the carton a substantially smooth continuous inner surface is provided throughout the side walls and corners of the carton as shown in Figures 3 and 4. It is thus possible to seal the membrane to the smooth ends of the corner portions 6 adjacent each of the open ends of the carton so as to ensure a tight seal at this region as well as the side wall regions of the carton adjacent each end thereof.

- 1f a carton is used having the score lines 5 Aextending the entire length of the side walls it is possible to smooth out the entire inner periphery of the carton adjacent each open end by means ofthe apparatus disclosed in copending application Serial No. 92,344, iiled May 10,l

1949, so that when the membrane is sealed in the end of the carton as previously described sufficient pressure is applied during the seal- -ing operation to smooth out the score lines 5 in the region B so that a continuous inner pefriphery is provided adjacent each end of the carton where the depressed portions 2| of the membrane 2B are adhered and sealed to the inner carton walls and corners.

In View of the fact that the membrane 20 flexible, normal manufacturing variations in the -dimensions of the perimeter of the carton opening :resulting from gluing and other forming operations or variations in the location of the side seam are avoided. The membrane 2U is preferably ynot provided with an predetermined score lines,lbut it can be readily shaped, formed, and depressed within the end of the carton and readily applied by heat and pressure to 'the inner surfaces of the carton walls and flaps as previously explained. In effect each sealing membrane is shaped and formed in situ just prior to sealing operation using the end of the container as a die or former so that the individual membrane will be given the exact complemental contour andv dimensions of the inner perimetrlc opening adjacent the open end of the container. 'Ihus a perfect seal is ensured as each portion of the membrane in contact. with the inner surfaces of the container will be in snug contact without any subsequent tension orv pull acting normally to separate the membrane from the contacting areas. Thus even though slight variations in the dimensions and contour may occur in the open end of each container in n ormal manufacturing operations the sealing membrane applied to each container is formed or shaped to the precise contour of each slight variation of the container and dimension andy contour that may be present in the particular individual container being sealed. The closure membrane, formed either of a self-sustaining thermoplastic film or of a sheet material provided with a thermoplastic coating of suitable thickness, will provide a hermetic seal at the ends of the container when sealed into position in the manner previously described by heat and pressure. It is preferred to use a sealing temperature as near as possible to the melting point of the thermoplastic lm or coating to minimize dissipation or absorption of the sealing medium into the side walls and flaps of the container. This provides a maximum viscosity or consistency of the thermoplastic substance of the membrane when the seal is formed thus ensuring a complete closure even though variations may occur in the perimetric contour and dimensions of the open end of the .container which normally occur in commercial containers. It is also important to select a membrane which has adequate bursting strength and stretch so as to withstand mechanical strains when the membrane is deformed during sealingl operations. The membrane should also retain its flexibility and strength in the nal sealed package. When the membrane is formed of coated sheet materials it is also important to select the components of such coated sheet to ensure anchorage of the coating so that it will not separate or loosen from the base sheet when exposed to the materials within the package.

When the sealing membrane is shaped and sealed into the end of the carton in the manner described it will have a slight slack and v yield sufiiciently under lthe pressure of the contents 40 without loosening any of the seams or sealed areas of the membrane, thus ensuring a leakproof seal. It will be readily apparent that the flexible seal thus provided is eifective in any tubular container of polygonal cross-section, i. e., having angularly disposed wall sections, regardless of whether any secondary closure member is used for the carton or, if any,' what style of secondary closure is used, as for example an inserted cap typei, telescoping cover, or locking flaps as shown in my preferred embodiment. Where locking flaps are used, it will be noted thatthe membrane is sealed to the inner surface of the carton around the entire periphery B just below the open end of the carton as well as at the adjacent areas 23 of the closure flaps. The

sealing of the membrane at these two regions thusY ensures a perfect hermetic seal at the end of the carton. In the event of any accidental loosening of the seal at the area 23 the sealed area in the adjacent region I3 of the flaps will thus serve as a secondary safety seal.

After the membrane is sealed in position as shown in Figure 1, the closure flaps I i are folded over the membrane, as illustrated in Figure 6,

and glued or sealed'together. The carton is then filled with any suitable liquid 40, or other material to be packaged and the open end thereof is sealed with another flexible membrane 2|! in the sameA manner as previously described so as to produce the completedsealed package. Such package is leak-proof. very strong, and will withstand considerable abuse in handling without developing any leakage.

The carton may be formed from any suitable material depending upon the type of materials to be packaged therein. The carton may be lined, for example, with greaseproof paper, wetstrength paper, wax paper, metal foil, rubber hydrochloride, regenerated cellulose and the like. The inner face of the carton may also be provided, if desired, with any suitable types of thermoplastic heat-sealable coatings. It may be treated with greaseproof and moistureproong agents. In the event the carton is used for packaging powders it may not be necessary to treat the inner face of the carton at all where siftproofness is merely required.

An essential feature of the present invention resides in providing and positioning the iiexible membrane so that it will contact and be sealed at the corners of the carton. Another is that where secondary closure flaps I I are used the membranes be positioned below the score lines. on which the closure flaps I I are hinged. By providing a complete seal below the score line at each end of the carton, a perfect seal is provided so that no leakage can occur. All the components of the package, that is the carton and the membranes, can be shipped in knocked-down or fiat condition to the user, so that shipping costs are reduced to a minimum. The package can be readily formed by automatic, semi-automatic, or hand equipment. All that is necessary is to set up the tubular container, and to seal the flexible membrane at one end thereof in the manner previously explained, after which the closure iiaps are folded and glued together. The carton can then be filled with any material desired to be packaged and the open end. thereof is then sealed with another flexible membrane in the same manner as previously described and the closure flaps are then folded and glued or sealed to form the completed package.

Obviously numerous modifications and the essential features of this invention may be made ip the package as well as in the mode of making same. It is intended to include such modifications within the scope of the appended claims.

I claim:

1. A package comprising a rectangular container formed of side walls hinged along score lines and having open ends, end iiaps hinged to each of said side walls for closing said ends, said score lines terminating short of the open ends to provide a substantially smooth inner periphery adjacent said open ends, and a flexible closure membrane extending entirely across the ends of said container and sealed thereto, said membrane being depressed adjacent the open end of the said container and adhered to the inner wall portions thereof adjacent the open ends thereof for providing a leakproof closure, and said end flaps being folded over said closure membranes.

2. A package comprising a rectangular container formed of side walls hinged along score lines and having open ends, an end flap hinged to at least one of said side walls for closing one of said ends, said score lines terminating short of the open end having said flap to provide a substantially smooth inner periphery adjacent said open end, and a iiexible closure membrane extending entirely across said open end of said container and sealed thereto, said membrane being depressed adjacent said open end of said container and adhered to the inner Wall portions thereof adjacent said open end thereof for providing a leakproof closure, and said end iiap being folded over said closure membrane.

ROBERT A. FARRELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

